Sunday February 12, 2012Handling stroke
The Doctor Says
By Dr MILTON LUM
The management of stroke and 'mini-strokes'. THE brain's functions depend on a constant blood supply for the oxygen and nutrients needed by its cells. The restriction or stoppage of this supply leads to damage and possibly death of the brain cells.
A stroke, which is also called a cerebrovascular accident (CVA), is a condition in which the blood supply to a part of the brain is cut off.
A transient ischaemic attack (TIA) is due to a temporary interruption of the blood supply to part of the brain, leading to a "mini-stroke". Its features are similar to that of a stroke, but the duration is about a few minutes. The TIA usually resolves within 24 hours.
TIAs provide a warning that further TIAs or a stroke is on the way.
The incidence of TIA is not well known as many people who have TIA do not seek medical attention.
It has been estimated that without treatment, the likelihood is one in 10 that a stroke will occur within a month after a TIA. As strokes lead to disability and even death in some instances, TIAs should be treated as seriously as strokes.
Strokes and TIAs are medical emergencies, and the earlier management is instituted, the less likely will be the damage to the brain, and consequently, the affected part of the body.
Making a diagnosis
There are two main types of strokes.
Ischaemic strokes, which comprise the majority of stroke cases, occur when the blood supply to the brain stops because the vessel is blocked by a blood clot. This may be due to thrombosis, in which a blood clot forms in one of the brain's arteries, or to an embolism, in which a blood clot formed elsewhere in the body gets into the brain's arteries to reach a blood vessel small enough to block its passage.
Haemorrhagic strokes occur when bleeding results from the bursting of a blood vessel supplying the brain because of weakness in its wall. The blood collection compresses the brain, causing damage and loss of function.
The diagnosis of stroke and TIA is made from a detailed history-taking, physical examination and selected diagnostic tests. The history provides vital information, and every effort should be made to obtain information from the patient, family members, friends, or witnesses.
The diagnosis provides answers to questions about the type of stroke, its site in the brain, the extent to which the brain is affected, why it occurred, as well as the potential complications and prognosis.
The investigations for stroke and TIA have been discussed in previous articles. Imaging tests like computerised tomography (CT) scan and magnetic resonance identify the type of stroke and TIA, its location in the brain and the extent to which the brain is affected.
Ultrasound examination of the heart (echocardiogram) or carotid artery in the neck (Doppler scan) help to identify causes of stroke and TIA. Dye may be injected into the carotid or vertebral arteries (arteriography) to enable a detailed examination of the arteries in the brain.
Other tests include blood tests like clotting factors, glucose and cholesterol, electrocardiogram to detect any abnormal heart rhythms, and chest and other x-rays to exclude other medical conditions.
Managing ischaemic strokes
The restoration of perfusion to the ischaemic brain is a vital therapeutic strategy. Although a core of brain tissue might not be salvageable in a stroke, the adjacent dysfunctional tissue may be saved if its circulation is restored and metabolism is normalised.
Ischaemic strokes are treated with medicines that dissolve blood clots (thrombolysis). These medicines are effective if given intravenously within about three to four hours after the onset of the stroke. After that, the medicine has not been shown to have beneficial effects. The earlier thrombolysis is instituted, the better the likelihood of recovery. However, thrombolysis cannot be prescribed for all patients.
Patients will also be prescribed aspirin, which reduces the stickiness in platelets, thereby reducing further blood clot formation. Other medicines will be prescribed if there is allergy to aspirin.
Some patients may be prescribed blood thinning (anti-coagulant) medicines, i.e. heparin or warfarin, that alter blood composition to prevent blood clot formation. However, the use of heparins is not routinely recommended as it does not reduce the mortality in patients with ischaemic stroke.
Anticoagulants are often prescribed in those with an irregular heartbeat.
Ischaemic strokes that are due to narrowing (stenosis) of the carotid artery in the neck are treated surgically, especially if the stenosis is severe. A surgical incision is made in the neck and the fatty deposits in the carotid artery removed.
Management of haemorrhagic strokes
Haemorrhagic strokes are managed by emergency surgery to remove blood from the brain and to ligate any burst blood vessels. The procedure, called a craniotomy, involves a surgical incision of the skull to allow access to the bleeding site(s). After the blood collection has been removed and any bleeding stopped, the bone removed from the skull will be replaced.
The patient may need to be put on a ventilator in the intensive care unit to assist his or her breathing. Medicines will also be prescribed to reduce the likelihood of further strokes, e.g. medicines to lower blood pressure and reduce swelling of the brain (cerebral oedema).
General management of strokes
The objectives are to provide supportive care and treatment of acute complication(s) in order to avoid mortality and functional disability.
Oxygen and airway support are necessary to ensure adequate tissue oxygenation and potential worsening of brain injury.
Regular monitoring and observations are necessary for detection of impaired lung and circulatory function. As high blood pressure is common following a stroke, it is gradually reduced with various medicines.
As there is an association between raised blood sugar following an acute stroke and subsequent mortality and impaired recovery, whether in diabetics or non-diabetics, it is vital that the blood sugar be well controlled.
Strokes may lead to impaired swallowing and consequent aspiration, which increases mortality. As such, a water-swallowing test is performed in all stroke patients before they are allowed to drink or eat. Incomplete oral-labial closure or a coughing reflex is indicative of an increased risk of swallowing. If the patient fails the swallowing test, a nasogastric tube is inserted for feeding.
When a fever occurs, doctors will localise the infection. Antibiotics are prescribed for infections, especially of the lungs and urinary tract, which are the commonest complications after a stroke.
Urinary catheters are avoided, if possible. Anti-pyretics are prescribed for fever, which is also associated with an increased risk of mortality and morbidity.
The majority of stroke patients are prescribed bed rest initially. Mobilisation is initiated as soon as the patient's condition is stabilised (to prevent complications). Frequent turning, alternating pressure (ripple) mattresses and passive and full-range-of-motion exercises are beneficial.
There has to be close skin monitoring for early detection of bed sores and measures have to be taken to avoid falls.
Management of TIA
The objective is to address the risk factors that led to TIAs in order to prevent a stroke from occurring.
The treatment prescribed depends on the cause(s) of the TIA. High blood pressure, which is the single most important risk factor, is treated with hypotensive medicines.
High blood cholesterol levels are treated with diet, exercise and statins.
Diabetes is treated with diet, exercise, oral hypoglycaemic agents or insulin.
Smoking cessation is vital as smoking doubles the likelihood of TIA or stroke because of the chemicals in the cigarette.
Carotid artery stenosis may require surgery (endarterectomy) to remove the fatty plaques.
Time is of the essence
The effective treatment of stroke and TIA saves lives and prevents long-term disability. The window of opportunity is no more than three to four hours in the case of stroke. Therefore, it behoves everyone with risk factors of stroke and TIA and their caregivers to remember that time is of the essence. In short, TIME = BRAIN.
Dr Milton Lum is a member of the board of Medical Defence Malaysia. This article is not intended to replace, dictate or define evaluation by a qualified doctor. The views expressed do not represent that of any organisation the writer is associated with.